1. Field of the Invention
The present invention relates in general to the semiconductor structural configuration of a bipolar junction transistor (BJT) and the process for its fabrication. In particular, the present invention relates to a BJT, and its process for fabrication, such that the BJT has improved current gain characteristics.
2. Technical Background
Conventional BJT's have limited current gain characteristics due to inherent limitations in their semiconductor structural configurations. FIG. 1 of the accompanying drawing shows schematically the cross section of a conventional BJT.
As is seen in FIG. 1, a conventional BJT is fabricated out of N-type substrate 1. P-well regions 10, although only one is shown in the drawing, are formed in N-type substrate 1 by methods known in the art. N.sup.+ -type emitter regions 12, as well as N+-type collectors 14, are formed in P-well 10 subsequently for the bipolar junction transistor. P-well contact regions 16, that is, the contact regions for the base regions are then fabricated thereon. Insulation layer 18 is formed on substrate 1 and metal contacts 20 are then formed.
Since, as is observed in the drawing, emitter region 12 is not sufficiently isolated from contact region 16 of base region 10, electrons flow, that is, a significant portion of the flow of negative carriers as emitted by emitter region 12, is absorbed by contact region 16 of base region 10. The desired electron flow from emitter to collector thereby decreases, causing the conventional lateral BJT device to exhibit current gain characteristics smaller than expected.